Hi,
I have a streaming program with the block as below [ref:
https://github.com/agsachin/streamingBenchmark/blob/master/spark-benchmarks/src/main/scala/TwitterStreaming.scala
]
1 val lines = messages.map(_._2)
2 val hashTags = lines.flatMap(status => status.split(" "
).filter(_.startsWith("#")))
3 val topCounts60 = hashTags.map((_, 1)).reduceByKey( _ + _ )
3a .map { case (topic, count) => (count, topic) }
3b .transform(_.sortByKey(false))
4a topCounts60.foreachRDD( rdd => {
4b val topList = rdd.take( 10 )
})
This batch is triggering 2 jobs...one at line 3b (sortByKey) and
the other at 4b (rdd.take) I agree that there is a Job triggered on line
4b as take() is an action on RDD while as on line 3b sortByKey is just a
transformation function which as per docs is lazy evaluation...but I see
that this line uses a RangePartitioner and Rangepartitioner on
initialization invokes a method called sketch() that invokes collect()
triggering a Job.
My question: Is it expected that sortByKey will invoke a Job...if
yes, why is sortByKey listed as a transformation and not action. Are there
any other functions like this that invoke a Job, though they are
transformations and not actions?
I am on Spark 1.6
Thanking You
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Praveen Devarao
Spark Technology Centre
IBM India Software Labs
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"Courage doesn't always roar. Sometimes courage is the quiet voice at the
end of the day saying I will try again"
